Micro-electro-mechanical valves and pumps

Abstract

Methods of fabricating micro-valves and micro-pumps. The micro-valves and micro-pumps that are fabricated include electrically conductive diaphragms fabricated from electrically conductive nano-fibers. Fluid flow through the micro-valves and pumping action of the micro-pumps is accomplished by applying electrostatic forces to the electrically conductive diaphragms.

1. A method of fabricating a micro-valve having an inlet and an outlet, said method comprising:
 on a substrate, forming a lower chamber having a bottom wall and sidewalls and forming an upper chamber having a top wall and sidewalls, a bottom of said upper chamber separated from a top of said lower chamber by a porous, flexible and electrically conductive mat of nano-fibers; 
 forming an opening in said top wall of said upper chamber; 
 forming an impervious valve seal on said mat of nano-fibers, said valve seat below and self-aligned to said opening; 
 forming a first electrically conductive plate above said top wall of said upper chamber and a second electrically conductive plate under said bottom wall of said lower chamber; 
 forming a first electrical contact to said first conductive plate; 
 forming a second electrical contact to said second conductive plate; 
 forming a third electrical contact to said mat of nano-fibers; 
 wherein said first conductive plate is formed on a insulating layer formed on a substrate; 
 wherein said forming said lower chamber includes forming a first trench in a first dielectric layer formed on said first conductive plate, filling said trench with a first sacrificial material and forming said porous mat of nano-fibers over said first sacrificial material followed by removing said first sacrificial material; and 
 wherein said forming said upper chamber includes forming a trench in a second dielectric layer formed on said mat of nano-fibers, filling said second trench with a second sacrificial material, forming a third dielectric layer on said second dielectric layer and said second sacrificial material, forming an opening though said third dielectric layer to said second sacrificial material and removing said second sacrificial material. 
 
   
   
     2. The method of  claim 1 , wherein said outlet comprises said opening in said top wall of said upper chamber and said inlet comprises an additional opening in said top wall of said upper chamber. 
   
   
     3. The method of  claim 1 , wherein a valve seat defined is by an edge of said opening along an interior surface of said top wall of said upper chamber. 
   
   
     4. The method of  claim 1 , further including:
 forming a valve seat on sidewalls of said opening. 
 
   
   
     5. The method of  claim 1 , further including:
 forming a protective coating on nano-fibers of said mat of nano-fibers. 
 
   
   
     6. The method of  claim 1 , wherein said micro-fibers are silicon filaments or carbon nanotubes. 
   
   
     7. A method of fabricating a micro-valve having an inlet and an outlet, said method comprising:
 on a substrate, forming a lower chamber having a bottom wall and sidewalls and forming an upper chamber having a top wall and sidewalls, a bottom of said upper chamber separated from a top of said lower chamber by a porous, flexible and electrically conductive mat of nano-fibers; 
 forming an opening in said top wall of said upper chamber; 
 forming an impervious valve seal on said mat of nano-fibers, said valve seat below and self-aligned to said opening; 
 forming a first electrically conductive plate above said top wall of said upper chamber and a second electrically conductive plate under said bottom wall of said lower chamber; 
 forming a first electrical contact to said first conductive plate; 
 forming a second electrical contact to said second conductive plate; 
 forming a third electrical contact to said mat of nano-fibers; 
 wherein a region of said top wall of said upper chamber adjacent to said opening is thicker than a region of said top wall of said upper chamber away from said opening; 
 wherein said first conductive plate is formed on a insulating layer formed on a substrate; 
 wherein said forming said lower chamber includes forming a first trench in a first dielectric layer formed on said first conductive plate, filling said trench with a first sacrificial material and forming said porous mat of nano-fibers over said first sacrificial material followed by removing said first sacrificial material; 
 wherein said forming said upper chamber includes forming a second trench in a second dielectric layer formed on said mat of nano-fibers, filling said second trench with a second sacrificial material, forming a first silicon nitride layer on said second dielectric layer and said second sacrificial material, forming a polysilicon layer on said first silicon nitride layer, forming a second silicon nitride layer on said polysilicon layer and forming an opening though said second silicon nitride layer, said polysilicon layer and said second silicon nitride layer to said second sacrificial material and removing said second sacrificial material; and 
 performing a thermal oxidation, said thermal oxidation converting a region of said polysilicon layer adjacent to said opening to silicon dioxide and pushing a region of said first silicon nitride layer adjacent to said opening toward said mat of nano-fibers. 
 
   
   
     8. The method of  claim 7 , wherein said outlet comprises said opening in said top wall of said upper chamber and said inlet comprises an additional opening in said top wall of said upper chamber. 
   
   
     9. The method of  claim 7 , wherein a valve seat is defined by an edge of said opening along an interior surface of said top wall of said upper chamber. 
   
   
     10. The method of  claim 7 , further including:
 forming a protective coating on nano-fibers of said mat of nano-fibers. 
 
   
   
     11. The method of  claim 7 , wherein said micro-fibers are silicon filaments or carbon nanotubes. 
   
   
     12. A method of fabricating a micro-valve having an inlet and an outlet, said method comprising:
 on a substrate, forming a lower chamber having a bottom wall and sidewalls and forming an upper chamber having a top wall and sidewalls, a bottom of said upper chamber separated from a top of said lower chamber by a porous, flexible and electrically conductive mat of nano-fibers; 
 forming an opening in said top wall of said upper chamber; 
 forming an impervious valve seal on said mat of nano-fibers, said valve seat below and self-aligned to said opening; 
 forming a first electrically conductive plate above said top wall of said upper chamber and a second electrically conductive plate under said bottom wall of said lower chamber; 
 forming a first electrical contact to said first conductive plate; 
 forming a second electrical contact to said second conductive plate; 
 forming a third electrical contact to said mat of nano-fibers; 
 forming an additional conductive plate on top of said upper chamber; 
 forming a third electrical contact to said additional conductive plate; 
 forming an additional opening into said bottom chamber, said inlet comprised of said additional opening and said outlet comprised of said opening; 
 wherein said first conductive plate is formed on a insulating layer formed on a substrate; 
 wherein said forming said lower chamber includes forming a first trench in a first dielectric layer formed on said first conductive plate, filling said first trench with a first sacrificial material and forming said porous mat of nano-fibers over said first sacrificial material followed by removing said first sacrificial material; and 
 wherein said forming said upper chamber includes forming a second trench in a second dielectric layer formed on said mat of nano-fibers, filling said second trench with a second sacrificial material, forming a third dielectric layer on said second dielectric layer and said second sacrificial material, forming a second conductive layer on said third dielectric, forming a fourth dielectric layer on said second conductive layer and forming an opening though said fourth dielectric layer, said second conductive layer and said third dielectric layer to said second sacrificial material and removing said second sacrificial material. 
 
   
   
     13. The method of  claim 12 , further including:
 forming a protective coating on nano-fibers of said mat of nano-fibers. 
 
   
   
     14. The method of  claim 12 , wherein said micro-fibers are silicon filaments or carbon nanotubes.